Maybe somebody has already mentioned this but it has always been my understanding that the highest pole highest to the left of the Lugo House in this now familiar photo of Calle de los Negros was one of the first lighting masts to be erected. One of three I think.
http://www.lafire.com/stations/PlazaStation/Plaza.htm
I read somewhere that they employed carbon filaments or carbon "sticks" actually, that had to be replaced daily after each nights use.